1. Field of the Invention
The present invention relates to a latch assembly applied to an instrument box and the like.
2. Description of the Prior Art
In a conventional latch assembly disclosed in Japanese Utility Model Laid-Open No. Sho 61-17635, an operating lever has its base-end portion pivoted to a bearing plate portion of a base plate through a first pivot. The bearing plate portion projects from an end portion of the base plate. A latch arm has its base-end portion pivoted to an intermediate portion of the operating lever through a second pivot. The second pivot and the first pivot are so arranged that the base plate is closer to the second pivot than to a straight line drawn between the first pivot and an engaging-end portion of a socket member in a locking condition in which a front-end hook portion of the latch arm engages with the engaging-end portion of the socket member.
In the conventional assembly, since there is no means for locking the operating lever to the base plate, there is a fear that the latch arm is accidentally disengaged from the socket member to accidentally unlock the wing element on a stationary frame element when a front-end portion of the operating lever hits against some other articles to have the operating lever swung up on the first pivot.
Further, in the conventional assembly, since there is no means for holding the operating lever in its projected or swung-up position, the operating lever stays in its lying-down position on the base plate. Under such circumstances, when the wing element is closed, the front-end hook portion of the latch arm hits against a front-surface portion of the socket member, and, therefore is not engaged with the engaging-end portion of the socket member. Consequently, after the wing element is closed, it is necessary for a user to: pull up the base-end portion of the latch arm by temporarily swinging the operating lever upward; move the front-end hook portion of the latch arm toward the engaging-end portion of the socket member; and, then swingably push down the operating lever, which makes it difficult to smoothly close the wing element and also makes it difficult to have the latch arm engaged with the socket member.
In addition, in the conventional assembly, since the socket member is fixedly mounted on the wing element, when the wing element, is misaligned with the stationary frame, it is not possible to cover a gap which is resulted from such misalignment to appear between the wing element and the stationary frame. This makes it difficult to have the latch arm engaged with the socket member. Even if the latch arm is engaged with the socket member, it is not possible to closely fasten the wing element to the stationary frame.